Munashe Chigerwe

Comparison of four methods to assess colostral IgG concentration in dairy cows

OBJECTIVE To determine sensitivity and specificity of 4 methods to assess colostral IgG concentration in dairy cows and determine the optimal cutpoint for each method. DESIGN Cross-sectional study. ANIMALS 160 Holstein dairy cows. PROCEDURES 171 composite colostrum samples collected within 2 hours after parturition were used in the study. Test methods used to estimate colostral IgG concentration consisted of weight of the first milking, 2 hydrometers, and an electronic refractometer. Results of the test methods were compared with colostral IgG concentration determined by means of radial immunodiffusion. For each method, sensitivity and specificity for detecting colostral IgG concentration < 50 g/L were calculated across a range of potential cutpoints, and the optimal cutpoint for each test was selected to maximize sensitivity and specificity. RESULTS At the optimal cutpoint for each method, sensitivity for weight of the first milking (0.42) was significantly lower than sensitivity for each of the other 3 methods (hydrometer 1, 0.75; hydrometer 2, 0.76; refractometer, 0.75), but no significant differences were identified among the other 3 methods with regard to sensitivity. Specificities at the optimal cutpoint were similar for all 4 methods. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that use of either hydrometer or the electronic refractometer was an acceptable method of screening colostrum for low IgG concentration; however, the manufacturer-defined scale for both hydrometers overestimated colostral IgG concentration. Use of weight of the first milking as a screening test to identify bovine colostrum with inadequate IgG concentration could not be justified because of the low sensitivity.

Effect of colostrum administration by use of oroesophageal intubation on serum IgG concentrations in Holstein bull calves.

OBJECTIVE To determine the amount of colostral IgG required for adequate passive transfer in calves administered colostrum by use of oroesophageal intubation and evaluate the impact of other factors on passive transfer of colostral immunoglobulins in calves. ANIMALS 120 Holstein bull calves. PROCEDURES Calves were randomly assigned to specific treatment groups on the basis of volume of colostrum administered and age of calf at administration of colostrum. Colostrum was administered once by oroesophageal intubation. Equal numbers of calves received 1, 2, 3, or 4 L of colostrum, and equal numbers of calves received colostrum at 2, 6, 10, 14, 18, or 22 hours after birth. Serum samples were obtained from calves 48 hours after birth for IgG determination by radial immunodiffusion assay. Effects of factors affecting transfer of colostral immunoglobulins were determined by use of a stepwise multiple regression model and logistic regression models. RESULTS A minimum of 153 g of colostral IgG was required for optimum colostral transfer of immunoglobulins when calves were fed 3L of colostrum at 2 hours after birth. Substantially larger IgG intakes were required by calves fed colostrum > 2 hours after birth. CONCLUSIONS AND CLINICAL RELEVANCE Feeding 100 g of colostral IgG by oroesophageal intubation was insufficient for adequate passive transfer of colostral immunoglobulins. At least 150 to 200 g of colostral IgG was required for adequate passive transfer of colostral immunoglobulins. Use of an oroesophageal tube for administration of 3 L of colostrum to calves within 2 hours after birth is recommended.

Cytologic and Histopathologic Evaluation of Extruded Canine Degenerate Disks

OBJECTIVE To describe the cytologic and histopathologic appearance of degenerate disk material in dogs with Hansen type I intervertebral disk disease (IVDD). STUDY DESIGN Case series. ANIMALS Dogs (n=45) that had surgical intervention for Hansen type I IVDD (January-November 2007). METHODS Impression smears and histopathologic sections were prepared from surgically removed degenerate disk material. All slides were evaluated for overall cellularity, quantity and attributes of extracellular matrix, types of cells present, and their cytomorphology. Histopathologic sections were also examined for presence of neovascularization and hemorrhage. RESULTS Cytologically, 11 of 45 samples consisted of only extracellular matrix, 30 had evidence of inflammation, and 20 contained dysplastic spindloid cells. Histologically, hyaline cartilage predominated in 35 of 45 samples, fibrocartilage in 4, and spindloid cells in 6; 37 of 45 were inflamed, 37 were hemorrhagic, and 13 had neovascularization. CONCLUSIONS The cytologic and histopathologic appearance of extruded degenerate disk material in dogs is variable and can include dysplastic spindloid cells. CLINICAL RELEVANCE The variability in cytologic findings and frequent presence of dysplastic spindloid cells suggest that cytology alone may not be a reliable tool to differentiate degenerate canine disk material from a mesenchymal neoplasm.

Evaluation of Fast Technology Analysis (FTA) Cards as an improved method for specimen collection and shipment targeting viruses associated with Bovine Respiratory Disease Complex

Abstract In order to improve the analytic quality of respiratory specimens collected from cattle for nucleic acid-based diagnosis, a study was undertaken to verify realtime PCR efficiency of specimens collected and stabilized on FTA Cards™, filter paper which is treated chemically. Nucleic acids collected using FTA Cards without the need for a cold-chain or special liquid media handling provided realtime PCR results consistent (96.8% agreement, kappa 0.923 [95% CI=0.89–0.96]) with the same specimens collected using traditional viral transport media and shipped on ice using the U.S. Department of Transportation mandated liquid handling requirements. Nucleic acid stabilization on FTA Cards was evaluated over a temperature range (−27°C to +46°C) for up to 14 days to mimic environmental conditions for diagnostic sample handling between collection and processing in a routine veterinary laboratory. No significant difference (P ≥0.05) was observed in realtime PCR cycle threshold values over the temperature range and time storage conditions for Bovine Viral Diarrhea virus, Bovine Respiratory Syncytial virus, Bovine Coronavirus, and Bovine Herpesvirus I. The four viruses evaluated in the study are associated with Bovine Respiratory Disease Complex where improvements in ease and reliability of specimen collection and shipping would enhance the diagnostic quality of specimens collected in the field, and ultimately improve diagnostic efficiency.

Evaluation of factors affecting serum IgG concentrations in bottle-fed calves.

OBJECTIVE To determine the effect of time interval from birth to first colostrum feeding on colostrum intake and serum IgG concentration and the effect of varying colostral volume intake and colostral IgG concentration on the probability of failure of passive transfer (FPT) in bottle-fed calves. DESIGN Randomized controlled study. ANIMALS 104 calves. PROCEDURES Equal numbers of calves were randomly assigned to groups and fed 3 L of their dams colostrum at 1, 2, 3, or 4 hours after birth by use of a nipple bottle. Calves were allowed to feed for 15 minutes, and intake was recorded. A second 3-L bottle feeding of colostrum was offered at 12 hours of age. RESULTS 17.2% of calves ingested 3 L of colostrum at the first feeding and 3 L at 12 hours of age. Calf age, up to 4 hours, had no significant effect on the calfs ability to ingest colostrum or on 48-hour serum IgG concentration. Colostral intake at 1, 2, 3, or 4 hours had no effect on intake at the second feeding. Probability of FPT in calves ingesting 3 L at both feedings was < 0.05. CONCLUSIONS AND CLINICAL RELEVANCE Allowing calves fed by nipple bottle to ingest as much colostrum as they can within 4 hours after birth and at 12 hours of age substantially reduced the probability of FPT. Bottle-fed calves that do not ingest 3 L of colostrum within the first 4 hours after birth should be targeted for oroesophageal intubation.

Frequency of detectable serum IgG concentrations in precolostral calves.

OBJECTIVE To determine the prevalence of detectable serum IgG concentrations in calves prior to ingestion of colostrum and to assess whether a detectable IgG concentration was related to dam parity, calf birth weight, calf sex, season of calving, or infectious agents that can be transmitted transplacentally. ANIMALS 170 Holstein dairy calves. PROCEDURES Serum samples were obtained from calves prior to ingestion of colostrum, and serologic testing for bovine viral diarrhea virus (BVDV) and Neospora caninum was performed. Relative risk, attributable risk, population attributable risk, and population attributable fraction for calves with a detectable serum IgG concentration attributable to positive results for N caninum and BVDV serologic testing were calculated. Logistic regression analysis was used to determine whether dam parity, calf sex, season of calving, and calf weight were associated with precolostral IgG concentration. RESULTS 90 (52.9%) calves had a detectable total serum IgG concentration (IgG >or= 16 mg/dL). Relative risk, attributable risk, population attributable risk, and population attributable fraction for calves with a detectable serum IgG concentration attributable to positive results for N caninum serologic testing were 1.66, 0.34, 0.014, and 0.03, respectively. Calf sex, calf birth weight, and season of calving were not significant predictors for detection of serum IgG in precolostral samples. CONCLUSIONS AND CLINICAL RELEVANCE Prevalence of IgG concentrations in precolostral serum samples was higher than reported elsewhere. There was no apparent link between serum antibodies against common infectious agents that can be transmitted transplacentally and detection of measurable serum IgG concentrations.

Comparison of colostrum feeding by nipple bottle versus oroesophageal tubing in Holstein dairy bull calves

OBJECTIVE To compare the apparent efficiency of absorption of IgG and failure of passive transfer of immunity rates between calves fed colostrum by nipple bottle (NB) and oroesophageal tubing (OET). DESIGN Randomized controlled study. ANIMALS 26 Holstein bull calves (age, 4 to 8 hours). PROCEDURES Calves were randomly assigned to receive colostrum by either NB or OET. Pooled colostrum was used for feeding each group of calves. Calves received either a maximum of 4 L of colostrum fed through an NB over a period of 20 minutes or an equivalent volume of colostrum fed by OET. Subsequently, a pair of similarly aged calves received similar volumes of colostrum with similar immunoglobulin concentrations. Colostrum was fed only once. Thereafter, calves were fed 2 L of milk replacer every 12 hours. All calves survived to at least 48 hours of age. Serum samples were collected prior to feeding colostrum and at 48 hours of age for determination of serum immunoglobulin concentrations. RESULTS There were no differences in failure of passive transfer of immunity rates and apparent efficiency of absorption of IgG between calves fed by NB or OET. Volume of colostrum fed was the only significant variable in determining failure of passive transfer of immunity in calves at 48 hours. CONCLUSIONS AND CLINICAL RELEVANCE Reported advantages and disadvantages of either feeding method are likely to be of minimal practical relevance in achieving adequate passive transfer of immunity in calves when calves are fed a similar volume of colostrum with comparable immunoglobulin concentrations.

Atypical Coccidiosis in South American Camelids

Reported clinical signs of coccidiosis in South American camelids include anorexia of a few days duration, sudden death, and diarrhea. Antemortem diagnosis of clinical coccidiosis is usually based on clinical signs and supported by detection of coccidial oocysts in feces. This report describes 2 atypical cases of coccidiosis in South American camelids that had no coccidial oocysts detected on antemortem fecal flotation, prolonged weight loss, and normal fecal consistency.

Comparison of serum immunoglobulin G half-life in dairy calves fed colostrum, colostrum replacer or administered with intravenous bovine plasma

Abstract In calves, passive immunity of immunoglobulins can be acquired through ingestion of colostrum or colostrum replacers. Plasma can been used to supplement immunoglobulins in healthy or sick calves. Serum half-life of colostral derived immuglobulin G (IgG) is estimated to be 20 days. Half-life of IgG is important in determining response to antigens and timing of vaccination in calves. To date studies evaluating half-life of colostrum replacer or plasma derived IgG are lacking. The objectives of this study were to compare the serum half-life of IgG derived from colostrum, colostrum replacer and plasma in dairy calves reared up to 35 days of age. Thirty Jersey calves were randomly assigned to receive colostrum or colostrum replacer by oroesophageal tubing or plasma by intravenous administration. Serum samples were collected at 2, 5, 7, 10, 14, 21, 28 and 35 days. Serum IgG concentrations were determined by radial immunodiffusion. The results indicated that half-life for IgG in colostrum fed (28.5 days) or plasma transfused calves (27.3 days) was longer than colostrum replacer fed calves (19.1 days). Further studies are required to evaluate pathogen specific immunoglobulins in order to recommend vaccination timing in calves fed colostrum replacers.

Refractometer assessment of colostral and serum IgG and milk total solids concentrations in dairy cattle.

BackgroundEstimation of the quantity of colostral IgG or serum IgG absorbed following ingestion of colostrum by calves is essential for monitoring the effectiveness of colostrum feeding practices on dairy farms. Milk total solids concentrations determination is a critical part of quality assessment of nonsaleable whole milk prior to feeding to calves. To date, on-farm methods to assess colostral IgG, serum IgG or milk total solids concentrations have been performed separately with various instruments. The objective of this study was to evaluate the diagnostic performance of a single electronic, hand-held refractometer for assessing colostral and serum IgG concentrations and milk total solids in dairy cattle. Colostral IgG, serum IgG and milk total solids concentrations were determined by the refractometer. Corresponding analysis of colostral and serum IgG concentrations were determined by radial immunodiffusion (RID) while milk total solids were determined by spectrophotometry. Sensitivity and specificity of the refractometer for colostrum and serum samples were calculated as determined by RID. Sensitivity and specificity of the refractometer for milk samples was calculated as determined by spectrophotometry.ResultsThe sensitivity of the refractometer was 1 for colostral IgG, serum IgG and milk total solids determinations. Specificity of the refractometer was 0.66, 0.24 and 0 for colostral IgG, serum IgG and milk total solids determinations, respectively. The refractometer underestimated colostral IgG, serum IgG and milk total solids concentrations compared to the concentrations determined by RID or spectrophotometry.ConclusionsThe refractometer was an acceptable, rapid, convenient on-farm method for determining colostral IgG and milk total solids. The refractometer was not an acceptable method for determination of serum IgG concentrations as it severely underestimated the serum IgG concentrations.